Experimental Investigation on Droplet Evaporation and Leidenfrost Phenomenon

Abstract

This experiment presents a detailed and thorough parametric study of the Leidenfrost point which serves as the boundary of the transition and film boiling regimes. The evaporation time in film boiling region of a sessile drop of liquid on a hot metallic surface has been analyzed in the present study. The time of evaporation for the droplet on the hot metallic surface was measured. With the time-temperature plot of these experimental data, the Leidenfrost phenomena has been clarified and explained. In the boiling curve for liquid, just after the transition boiling region and before the film boiling region, the heat transfer approaches its minimum value. The corresponding temperature of this minimum value was termed as the Leidenfrost temperature and the phenomenon is known as Leidenfrost phenomena. Sessile drop of four different liquids namely Distilled Water, Acetone, Methanol and Ethanol having diameters 1.5mm, 2.25mm, 4.5mm were used to conduct the experiment for a wide range of solid surface temperatures of 50-350⁰C. Three solid surfaces namely Brass, Aluminum and Mild Steel were used to conduct the experiment. The graph we plotted by placing evaporation time of liquids against surface temperature of metal blocks is exactly the opposite to the conventional boiling curve. The temperature at which time required for evaporation is maximum is called the Leidenfrost point. These variations in Liquid types, Diameter of drops and Metals have been done to present a clear statement that the Leidenfrost temperature range does not change. The only change obtained from varying liquid, diameter and metal is the time of evaporation. So for all the metal blocks and test liquids of different diameters used in our experiment, Leidenfrost temperature is within the range 170-210⁰C. This concludes to the fact that Leidenfrost point does not change for any parameter.